Israeli tank fire killed a Palestinian woman in her Gaza home on Thursday, in the second day of the worst clashes between Israeli and Palestinian armed groups since the devastating 2014 war.
The confrontation came after a new cross-border tunnel was discovered reaching into Israel from the Palestinian enclave.
Since the clashes broke out, Hamas and other militant groups have fired bullets and mortar rounds on at least 10 occasions and the Israeli air force has carried out at least three bombing raids.
Israeli tanks stationed on the border have also fired multiple times at what the army said were Hamas targets.
Hamas mlitants fired mortar shells at Israeli forces working to unearth the tunnel and Israel responded with tank fire and air strikes, an army spokeswoman said.
Late on Thursday afternoon, tank shelling that followed a mortar attack from the Khan Yunis area in southern Gaza killed Zeina Al-Amour, 54, according to Nasser hospital that pronounced her death.
A 21-year-old was also wounded in artillery shelling in the area.
Overnight air raids wounded four people, three of them children, medical and security officials said.
The flare-up has raised concerns over the fate of a ceasefire between Israel and Hamas, which controls Gaza, that has held since the 50-day military campaign by Israel.
That conflict claimed the lives of over 2,100 Palestinians, most of whom were civilians, while 67 Israeli soldiers were also killed along with six Israeli non-combatants.
Lieutenant-Colonel Peter Lerner, an Israeli military spokesman, said a new tunnel about 30 metres (100 feet) deep was discovered on Thursday and that an investigation was under way to determine whether it was dug before or after the war.
But the armed wing of Hamas said the tunnel was not new and had been in use in the early part of the war in 2014.
Defence Minister Moshe Yaalon said after touring the area that Israel would not be deterred by Hamas's threats and would continue to search "until all the tunnels are found."
A senior Hamas official, Khalil al Hayya, said efforts by Qatar and Egypt were ongoing to try to restore calm, but he warned that "Israeli incursions into Gaza would not be tolerated."